A chemical container has exploded in Buenos Aires, Argentina, blanketing the capital in a huge toxic cloud. Residents are being told to stay inside while a mass evacuation from the area surrounding the blast has been ordered, local media report.

The container filled with pesticide caught on fire after a chemical reaction between its contents and exploded. As the flames were put out, yellow smoke billowed out of it. City officials believe the container may have been transporting garbage.

"The pesticide presents a low level of danger and affects the respiratory tract," said Sergio Berni, the national Security Secretary, as quoted by C5N television channel.

The incident hit the city's Port Terminal 4 early in the morning. Several buildings in the port and the surrounding area were evacuated, according to Buenos Aires's Civil Defense. Residents in near-by areas were told to stay indoors, close their windows and turn off air conditioning.

By 9:00am local time a strange heavy odor, described as similar to burnt oil or a gas leak, hit the city causing some metro lines and the city's domestic airport to suspend operations.

A public health and security emergency has been declared by the country's Security Ministry in the wake of the incident, reports Buenos Aires Herald. The ministry urged the public to call 107 in the event of any intoxication symptoms.

Some residents complain of eye irritation and breathing problems and have to move along the streets covering their faces with masks and handkerchiefs, but officials say "the situation is under control" now.